Heat the oil in a large pan over low heat. Saute the onions with the salt for 8 minutes, stirring frequently, until they are soft. Add the tomatoes and raise the heat to medium low. Continue to cook for 30 minutes, stirring occasionally, just until the vegetables are tender and the liquid is almost completely evaporated. Remove and reserve.
In a large paella pan or similar, heat the oil over medium-high heat. Add the artichoke hearts and saute until golden, about 6 minutes. Add the cauliflower and cook until lightly colored, about 3 minutes.
Add the rice and garlic and stir continously to toast the rice and lightly brown the garlic, about 2 to 3 minutes. Stir in the sofrito.
Add enough vegetable stock to cover the rice, about 2 cups. If using fresh peas, add those now. Add sea salt and black pepper. Bring to a boil, then reduce to medium low and simmer, uncovered, until the rice has absorbed most of the stock, about 15 minutes.
Add the rest of the vegetable stock and continue cooking until the rice has absorbed all of the liquid, about 12 minutes. If using frozen peas, add them during the last 6 minutes of cooking. The rice should be al dente when done. If it is too firm, add additional water ½ cup at a time and continue cooking until the rice is done. Keep the heat around medium-low to allow a gentle simmer. Taste and add more salt and pepper as necessary. When ready to serve, garnish with the roasted red pepper strips and chopped parsley.
Cooking time can vary based on how long it takes the rice to soak up the liquids. If desired, you can cover the paella pan with foil during the initial cooking to help keep moisture in, then finish with the foil off to achieve the bottom crust.